For creating novel electronic quantum devices, it is necessary not only to be able to fabricate nanometer-size elements, but also to ensure atomic smoothness of their surfaces and an opportunity of assembling them in well-reproducible 3D constructions perfectly controlled in all dimensions. In this connection, precise naturally occurring nanoshells (carbon nanotubes and fullerenes) attracts much attention of the researches. Recently, we have realized a new class of precise micro-and nanoshells - artificial solid-state shells of various shapes that offers much promise in fabrication of micro-and nanodevices. . In this report, we give an overview of our original works on the formation of cylindrical nanoshells (nanotubes, nanospirals and nanorings) from single-crystal 򤯓 and Si/GeSi heterolayers . New results on the formation of spatially periodic structures ,open and closed single-crystal nanoshells of various shapes with the minimum radius of curfature of ~1 nm are described.. A concept for nanoelectronics and nanomechanics exploiting artificial single-crystal nanoshells is presented. The following points are also considered : (i) method for crystal disassembling by monolayers (ii) formation of 3D shells with dimensions perfectly controlled in all (x,y,z) directions, (iii) bonding between contacting shells resulting in the formation of single-crystal walls, (iv) filling of shells with different materials and their overgrowth, (v) assembling the shells into more complex architectures ,(vi) self-formation of perfectly periodic structures, (vii)electrical and mechanical properties of micro- and nanoshells, Device applications of some phenomena and factors such as geometric effect and tunneling permeability of shells, including vertical ones, are demonstrated.